1. Field of the Invention
The invention relates to a BGA (ball grid array) type semiconductor device using a TAB (tape automated bonding) tape or the like as an interposer between an LSI chip and an external terminal, a tape carrier for a semiconductor device, and a semiconductor device using said tape carrier. More particularly, the invention relates to a BGA type semiconductor device of the so-called xe2x80x9cPSR via typexe2x80x9d wherein an insulating film of a photosolder resist (PSR) has been provided on a side, where a wiring pattern is provided, while leaving via holes (PSR via) for solder balls, a tape carrier for a semiconductor device, and a semiconductor device using the same.
2. Prior Art
In recent years, in various types of equipment using semiconductor devices, including particularly portable equipment and mobile equipment, a reduction in size and a reduction in weight have been advanced. Therefore, regarding semiconductor devices used in these types of equipment as well, there is a demand for a reduction in size and a reduction in thickness. To meet this demand, in recent years, packages having substantially the same size as semiconductor elements, called xe2x80x9cchip-size packagesxe2x80x9d (hereinafter abbreviated to xe2x80x9cCSPxe2x80x9d), have been proposed, and efforts have been made to commercialize semiconductor devices using these packages.
A BGA (ball grid array) type semiconductor device using a TAB tape as an interposer is shown as a representative example of these semiconductor devices in FIGS. 1 and 2.
This device is a BGA type semiconductor device of the so-called xe2x80x9cPSR via typexe2x80x9d wherein, while leaving via holes 12 for solder balls (PSR via), an insulating film 2 composed of a photosolder resist (PSR) is provided on a tape substrate 5, composed of an insulating film, on its side where a wiring pattern 3 is provided.
Specifically, FIGS. 1 and 2 show the construction of a conventional semiconductor device which is an object to be improved by the invention. A TAB tape 1 used in the semiconductor device comprises: a tape substrate 5 formed of a polyimide resin insulating film; a wiring pattern 3 which has been formed by bonding a copper foil onto one side of the tape substrate 5 through an adhesive 4 and photoetching the copper foil and has, on its one end, a bonding pad 10 for connection to a semiconductor and has, on its other end or in a portion between both ends thereof, a solder ball mounting pad 30; and an insulating film 2 in a predetermined PSR pattern which has been formed, on the surface of the wiring pattern 3 in the region of the solder ball mounting pad 30 while leaving a via hole 12 for a solder ball, by printing a photosolder resist resin by means of a printing plate on the wiring pattern 3 and subjecting the print to pattern exposure and development.
In the TAB tape 1 as a wiring tape for mounting a semiconductor element, for wire bonding purposes, a window hole is generally formed in the center portion by stamping, and the insulating film 2 is not formed in the portion of the bonding pad 10 on the tape substrate 5 and a region extended inward from the bonding pad 10.
In producing the semiconductor device, shown in FIG. 1, by using this TAB tape 1, a semiconductor chip 7 is applied through an adhesive 6 onto the tape substrate 5 in its side remote from the wiring pattern 3 (opposite side of the tape substrate 5), and an electrode 8 in the semiconductor chip 7 is electrically connected to the bonding pad 10 in the TAB tape through a bonding wire 9 formed of gold.
Next, the connection in the wire bonding, that is, the bonding lead portion, is sealed by a mold resin 11. Thereafter, solder balls 13 formed by reflow treatment are mounted respectively on the solder ball mounting pads 30 in such a manner that the solder balls 13 are arrayed in via holes 12 for solder balls.
According to this semiconductor device, a wiring pattern 3 is provided on the tape substrate in its side opposite to the side on which the semiconductor chip 7 in its element formation surface is put. This construction permits the element electrode 8 in the semiconductor chip 7 to be bonded to the wiring pattern 3 through the bonding wire 9 which is passed through the window hole 15. Therefore, the bonding wire 9 can be provided without being extended around the periphery of the semiconductor chip 7. This can eliminate the need to ensure, on the periphery of the semiconductor chip 7, a wiring space for the bonding wire 9 and thus can reduce the size and thickness of the whole device. Further, since wiring bonding can be carried out, a difference in coefficient of thermal expansion between the semiconductor element and the substrate can be absorbed by the bonding wire 9. This is advantageous, for example, in that an inexpensive resin substrate rather than an expensive ceramic substrate can be used.
However, it has been found that, in sealing the bonding lead portion by the mold resin, the mold resin spreads on the PSR pattern and flows into the via hole (PSR via) for a solder ball and, consequently, the solder ball disadvantageously comes off from the via hole.
Accordingly, it is an object of the invention to provide a BGA type semiconductor device which can solve the above problem of the prior art and can prevent the flow of a mold resin into a portion of a via hole for a solder ball through the provision of a groove.
It is another object of the invention to improve the effect of damming off a mold resin by a dam groove, which has been provided in such a form as not to expose the underlying wiring layer, and thus to improve the productivity of a tape carrier for a semiconductor device and a semiconductor device using the same.
According to the first feature of the invention, a BGA type semiconductor device comprises
a BGA type interposer comprising: a tape substrate formed of a resin insulating film; a wiring pattern, formed of a metal foil, provided on one side of the tape substrate; a bonding pad, for connection to a semiconductor, provided on one end of the wiring pattern; a solder ball mounting pad provided on the other end of the wiring pattern or in a portion between both ends of the wiring pattern; an insulating film provided on the surface of the wiring pattern in the region of the solder ball mounting pad while leaving a via hole for a solder ball; a window hole for wire bonding of the bonding pad to an electrode in a semiconductor element; and a groove portion which is a smaller-thickness portion of the insulating film provided in a part of the insulating film, for preventing the flow of a mold resin into the via hole for a solder ball,
a semiconductor element, provided with an electrode, mounted on the tape substrate, in the interposer, on its side remote from the wiring pattern, said electrode in the semiconductor element having been wire bonded to the bonding pad through the window hole, the connection between the bonding pad and the semiconductor element having been sealed with a mold resin by pouring the mold resin into the window hole while preventing the flow of the mold resin into the via hole for a solder ball by the groove portion, and
a solder ball mounted on the solder ball mounting pad.
According to this construction, by virtue of the provision of a groove portion, which is a smaller-thickness portion of the insulating film in a part of the insulating film, for preventing the flow of the mold resin into the via hole for a solder ball, in pouring the mold resin into the window hole used in wire bonding to perform sealing, even when the mold resin, which has been poured into the window hole, is likely to flow into the via hole for a solder ball, in which the solder ball mounting pad is present, from the window hole side, the mold resin first flows into the groove portion, whereby the flow of the mold resin into the via hole for a solder ball can be prevented by the groove portion. Therefore, the solder ball mounting pad is always maintained in an exposed state without being covered by the mold resin, whereby the problem of coming-off of the solder ball mounted on the solder ball mounting pad can be prevented.
In the BGA type semiconductor device according to the first feature of the invention, preferably, the groove portion is provided between the bonding pad and the via hole for a solder ball.
Preferably, the interposer is a TAB tape such that the tape substrate is formed of a polyimide resin, the metal foil is a copper foil, and the insulating film is formed of a solder resist.
Further, in the BGA type semiconductor device according to the first feature of the invention, the groove portion may be linearly provided along the window hole. Alternatively, the groove portion may be wavily provided along the window hole.
Further, the groove portion may comprise a plurality of independent grooves which have been successively arranged in a broken line form.
The groove portion may comprise a plurality of groove portions, adjacent to each other, provided, between the bonding pad and the via hole for a solder ball, so as to extend along the longitudinal direction of the window hole.
According to the second feature of the invention, a tape carrier for a semiconductor device comprises:
a tape substrate formed of a resin insulating film;
a wiring pattern, formed of a metal foil, provided on one side of the tape substrate;
a bonding pad, for connection to a semiconductor, provided on one end of the wiring pattern;
a solder ball mounting pad provided on the other end of the wiring pattern or in a portion between two ends of the wiring pattern;
an insulating film provided on the surface of the wiring pattern in the region of the solder ball mounting pad while leaving a via hole for a solder ball;
a window hole for wire bonding of the bonding pad to an electrode in a semiconductor element; and
a strip-shaped groove portion for preventing the flow of a mold resin into the via hole for a solder ball at the time of sealing, with a mold resin, of a connection, between the bonding pad and a semiconductor element, formed in the wire bonding of the bonding pad to an electrode in the semiconductor element, said strip-shaped groove portion having a flat shape in section and being provided along the window hole on the surface of the insulating film present between the window hole and the via hole, for a solder ball, close to the window hole.
According to this construction, since a groove is provided as a strip-shaped groove, which is flat in section, on the surface of the insulating film along the window hole, the ability to prevent the flow of the mold resin into the via hole for a solder ball is larger than that in the case where a plurality of narrow grooves in a stripe form are provided. Therefore, the flow of the mold resin into the via hole for a solder ball can be more effectively prevented.
In the tape carrier according to the second feature of the invention, preferably, the strip-shaped groove portion has a roughened bottom face.
According to this construction, since the strip-shaped groove portion has a roughened bottom face, the flow of the mold resin into the via hole for a solder ball can be more effectively prevented than the case where the groove has a smooth bottom face.
In the tape carrier according to the second feature of the invention, preferably, the insulating film has been formed from photosensitive resin layer, and the strip-shaped groove portion has been formed in such a manner that, in the step of exposure of the photosensitive resin layer, a mask having minute light shielding portions arranged at given intervals is provided, the photosensitive resin layer is cured in a form conforming to the minute light shielding portions, and the photosensitive resin layer in its portion remaining uncured is removed by development.
The strip-shaped groove portion may have been mechanically formed with a cutting blade.
The insulating film may have been formed by printing or atomization application of a photosensitive resin or dipping in a photosensitive resin.
According to the third feature of the invention, a semiconductor device comprises:
the above tape carrier;
a semiconductor chip, provided with an electrode, applied through an adhesive to the tape substrate, in the tape carrier, in its side (opposite side) remote from the wiring pattern, said electrode having been electrically connected to the bonding pad as a part of the wiring pattern through a bonding wire;
a mold resin for sealing a connection between the bonding pad and the semiconductor chip; and
a solder ball which has been mounted on the solder ball mounting pad in the via hole for a solder ball after the sealing of the connection with the mold resin.
According to the invention, by virtue of the provision of a strip-shaped groove portion, which is flat in section, on the surface of a part of the insulating film between the bonding pad and the via hole for a solder ball, along the window hole, for preventing the flow of the mold resin into the via hole for a solder ball, even when the mold resin, which has been poured into the window hole used in the wire bonding, is likely to flow into the via hole for a solder ball, in which the solder ball mounting pad is present, from the window hole side, the mold resin first flows into the strip-shaped groove portion, whereby the flow of the mold resin into the via hole for a solder ball can be prevented by the groove portion. In this case, since this groove portion is provided as a strip-shaped groove portion which is flat in section and thus has a large sectional area, the ability to prevent the flow of the mold resin into the via hole for a solder ball is very high. This can prevent the mold resin from covering the solder ball mounting pad present at the bottom of the via hole, for a solder ball and, consequently, the solder ball mounting pad is always maintained in an exposed state, whereby the problem of coming-off of the solder ball mounted on the solder ball mounting pad can be prevented.